PROCEEDINGS OF THE COTTESWOLD CLUB 215 



especially useful in the manufacture of tiles, cisterns, 

 pipes, slates, and so on, and it has, 1 believe, l)een even 

 used for railway sleepers. 



By other ingenious machinery, slag coming from the 

 furnaces is subjected to a process which turns it out in 

 small-sized pieces, which are called ''slag-shingle." These 

 are largely used in certain localities in making concrete. 

 Another machine, again, converts the molten slag into a 

 sort of spongy sand, and this slag sand is much used to 

 make slag bricks. The sand is simply mixed with 

 selenitic lime, and a small proportion of iron oxides ; it 

 then passes into a particular kind of brick press ; the 

 bricks are taken out of the presses by girls, placed upon 

 spring barrows and removed to air-hardening sheds. Here 

 they remain a week or ten days, after which they are 

 stacked in the air to further harden, and in five or six 

 weeks are ready for the market. We have here a curious 

 anomaly of bricks being made without burning, and of a 

 wet season being favourable to the hardening process. 

 They are very tough, do not split when a nail is driven 

 into them, are easily cut, do not break in transit, the frost 

 has no ejftect upon them, and they improve by age. 



Slag sand mixed with other materials is converted into 

 a first-rate cement ; and some samples, rich in lime, have 

 even been used with success as fertiHzers for the land. 



More than 20 years ago Sir Louthian Bell called 

 attention to the fact that 20,000 lbs. of phosphoric acid 

 were allowed to remain and injure 2,000,000 tons of 

 pig-iron then produced in England annually. By the 

 Thomas Gilchrist process this phosphoric acid is now 

 abstracted from the iron by lining the converter with 

 quick-lime. The large amount of phosphoric acid in the 

 slag so produced, amounting as it does in some cases to 

 over 18 per cent., at once attracted the attention of 

 Agricultural Chemists, and numerous patents were from 

 time to time taken out for the separation of that important 



